CIDR 子网掩码 反掩码 /30 255.255.255.252 0.0.0.3 /29 255.255.255.248 0.0.0.7 /28 255.255.255.240 0.0.0.15 /27 255.255.255.224 0.0.0.31 /26 255.255.255.192 0.0.0.63 /25 255.255.255.128 0.0.0.127 /24 255.255.255.0 0.0.0.255 /23 255.255.254.0 0.0.1.255 /22 255.255.252.0 0.0.3.255 /21 255.255.248.0 0.0.7.255 /20 255.255.240.0 0.0.15.255 /19 255.255.224.0 0.0.31.255 /18 255.255.192.0 0.0.63.255 /17 255.255.128.0 0.0.127.255 /16 255.255.0.0 0.0.255.255 /15 255.254.0.0 0.1.255.255 /14 255.252.0.0 0.3.255.255 /13 255.248.0.0 0.7.255.255 /12 255.240.0.0 0.15.255.255 /11 255.224.0.0 0.31.255.255 /10 255.192.0.0 0.63.255.255 /9 255.128.0.0 0.127.255.255 /8 255.0.0.0 0.255.255.255